[clang] [clang] Ensure `--print-runtime-dir` path exists (PR #102834)

[Reid Kleckner via cfe-commits]

https://github.com/rnk approved this pull request.

I found this at the bottom of my inbox after a long cleanout.

I'm struggling to remember it at this point in the evening, but we've done things like this before as part of the runtime path changes, and I don't see any reason to object to this one.

Part of me wants to test this behavior since we have the indirection layer, we don't have to copy the clang binary and create an entire runtime tree in the test directory, but I wouldn't block this over that concern.

In conclusion, I think we should merge the patch.

https://github.com/llvm/llvm-project/pull/102834